91Ó°ÊÓ

Be sure that you've familiarized yourself with the first set of formulas presented in this section by working \(1-4\) in the Concept and Vocabulary Check. In Exercises \(1-8,\) use the appropriate formula to express each product as a sum or difference. $$\sin 6 x \sin 2 x$$

Verify each identity. $$\sin x \sec x=\tan x$$

Use the formula for the cosine of the difference of two angles to solve. $$\cos \left(45^{\circ}-30^{\circ}\right)$$

In Exercises \(1-10,\) use substitution to determine whether the given \(x\) -value is a solution of the equation. $$\cos x=\frac{\sqrt{2}}{2}, \quad x=\frac{\pi}{4}$$

Be sure that you've familiarized yourself with the first set of formulas presented in this section by working \(1-4\) in the Concept and Vocabulary Check. In Exercises \(1-8,\) use the appropriate formula to express each product as a sum or difference. $$\sin 8 x \sin 4 x$$

Use the formula for the cosine of the difference of two angles to solve. $$\cos \left(120^{\circ}-45^{\circ}\right)$$

Verify each identity. $$\cos x \csc x=\cot x$$

In Exercises \(1-10,\) use substitution to determine whether the given \(x\) -value is a solution of the equation. $$\tan x=\sqrt{3}, \quad x=\frac{\pi}{3}$$

Be sure that you've familiarized yourself with the first set of formulas presented in this section by working \(1-4\) in the Concept and Vocabulary Check. In Exercises \(1-8,\) use the appropriate formula to express each product as a sum or difference. $$\cos 7 x \cos 3 x$$

Verify each identity. $$\tan (-x) \cos x=-\sin x$$